This invention relates to a device for enabling a load to be moved along a path defined by a guide member or a series of guide members, freely past support are attachment points for the guide member or members. Such a device is described in my British Patent Specification No. 1582201 and corresponding U.S. Pat. No. 4,265,179 and the present invention provides improvements in the devices disclosed in that specification, particularly with a view to providing constructions which enable the device to withstand heavier loadings.